Acid Attacks
This lesson looks at the effect of pH in a pond on the organisms that live there.
The pH of ponds can differ depending on their location and the source of their water. pH levels
are not static within ponds, however, and can fluctuate throughout the course of a day. The
change in pH in a pond does not need to be large for the organisms living in it to be affected in
quite significant ways.
Resources
•
Powerpoint presentation (see end of pdf)
•
Teachers’ notes to support the presentation (see end of pdf)
pH in Ponds – Acids attack
• A pond can vary in many ways,
one of which is how acid or alkali
the water is. This can be due to
the type of soil or rock the pond is
on, how much carbon dioxide is in
the air, acid rain or even the type
of plants present.
• A high pH (alkaline conditions)
favours some species while low
pH (acid conditions) favours other
species.
• Most animals with a shell such
as snails and crayfish can only
survive in alkaline water, while
some mosses prefer acidic water.
Click here to watch a
short film introduction to
ponds
Starter: Where would you be more likely to find these organisms in an slightly acidic pond
or a slightly alkaline one?
Whirly-gig
beetle
Pond Snail
Moss
Swamp Spider
Go to the next slide once you have decided your answers
ACID
ALKALI
Starter: Where would you be more likely to find these organisms in an slightly acidic pond
or a slightly alkaline one?
Whirly-gig
beetle
Pond Snail
Answers
Tends to be upland ponds on acid soils,
some mosses can also increase acidity
Moss
Swamp Spider
Tends to be lowland ponds on chalky
soil, snails need calcium from alkaline
chalk to make their shells
ACID
Moss
ALKALI
Swamp
Spider
Whirly-gig
beetle
Pond Snail
Challenge:
You are going to sample a pond to observe how pH affects the type of organisms (living
things) in and around acidic or alkaline ponds.
Equipment needed:
white dish or
tray at least
5cm deep
Pond net
Plastic gloves
pH test kit
Camera, notebook,
Identification guide
book/internet guide
Need to know beforehand:
1) Don’t get any of the pH indicator in the pond, it will damage the ecosystem
2) Make sure you remove samples carefully and replace all animals and plants back where
you found them. Don’t just throw the water from the tray back in, lower your tray to the
water level to empty it. Throwing a pond skater back into the water from 1 metre high would
be like dropping you off the London Eye!
Challenge:
You are going to sample the pH of your pond and sample the pond life to find out how pH
can affect the type of organisms that live there.
Method:
1) Gloves on to protect you and the samples.
2) Fill your test tube with water from the pond you
are sampling, allow it to settle for 30 seconds.
3) Place 5 drops of Universal indicator into the test
tube and record the pH.
4) Do not put the test tube water with Universal
indicator back into the pond, dispose of it down a
sink!
5) Repeat this 3 times with samples from different
parts of the pond.
6) Now record all the livings things you can find with
your net, if you don’t know their name describe
them, take photos or make sketches.
Conclusions:
1. What was the pH of your pond?
2. What kinds of organisms did you find in the pond?
3. Why might the pH change through the day and night?
4. What might increase the amount of CO2 in the water and how does this affect pH?
5. Were there any snails present?
6. Was there a significant amount of moss or algal growth?
7. What might change the pH of a pond?
pH in Ponds – Acids Attack
Age group: 12-16 years (the resource is adaptable for different levels as required by the facilitator)
Curriculum links and keywords: pH, Acids, Alkalis, aquatic life, adaptations
Group size: up to 30 students
Locations: anywhere with a pond or static water that is safe to access and a classroom
Time needed: 1 hour
Learning outcomes: For students to recognise that a pH can affect the species found in a pond
community.
Note: No specialist knowledge is required but students will need to have prior knowledge of acids
and alkalis
Preparation white dish or tray at least 5cm deep, pH test kit, plastic gloves, camera, notebook,
Identification guide book/internet guide, notebooks, pencils.
Activity
1) Open the PowerPoint included in this download
Basic info:
•
A pond can vary in many ways, one of which is how acid or alkali the water is. This can be due to
the type of soil or rock the pond is on, how much carbon dioxide is in the air, acid rain or even the
type of plants present.
•
A high pH (alkaline conditions) favours some species while low pH (acid conditions) favours
other species.
•
Most animals with a shell such as snails and crayfish can only survive in alkaline water, while
some mosses prefer acidic water.
Slide 1: The PowerPoint begins with an introductory video clip to ponds (click on the link in the
PowerPoint to open the video which is already loaded onto YouTube). To preview the clip see:
http://www.youtube.com/watch?v=STasskXuUiQ&feature=channel_video_title
Slides 2, 3: Starter activity on pH specific species with answers
Slide 4: Introduces the challenge activity where students sample a pond to observe how pH affects
the type of organisms (living things) in and around acidic or alkaline ponds. It Includes a “need to
know section” on avoiding sample damage.
Slide 5: Challenge instructions and method.
Slide 6: Conclusion questions.
Questions for students to consider:
1. What was the pH of your pond?
2. What kinds of organisms did you find in the pond?
3. Why might the pH change through the day and night?
4. What might increase the amount of CO2 in the water and how does this affect pH?
5. Were there any snails present?
6. Was there a significant amount of moss or algal growth?
7. What might change the pH of a pond?